Scraped-surface heat exchangers and similar apparatus employing hinged blades to scrape a fluid being processed from an elongated cylindrical wall or exemplified in U.S. Pat. Nos. 2,281,944, 2,235,002, 3,385,354, 3,568,463, and 3,848,289; cf. U.S. Pat. No. 2,776,765, which shows fixed blades. Various uses of such apparatus are described in A. E. Bailey, INDUSTRIAL OIL AND FAT PRODUCTS (3rd edition, Interscience Publishers, Division of John Wiley & Sons) at pages 1066 et seq. and in Bulletin V300 entitled "VOTATOR.RTM. Scraped Surface Heat Exchangers" and published by Chemetron Corporation, P.O. Box 35600, Louisville, Kentucky 40232.
Such apparatus generally comprises a chamber having an elongated cylindrical wall, within which a shaft is rotatable concentrically, and scraper blades are hinged to the shaft, as by radial pins. In some apparatus, the blades are biased by separate springs into edge contact with the wall.
As manufactured and sold by Chemetron Corporation, such apparatus often are several feet or more long with a ratio between eight and twenty-four of overall length to inner diameter of the wall. In prior apparatus, particularly horizontal apparatus as commonly used as scraped-surface heat exchangers, the ratio has been limited so as to avoid excessive flexure and consequent misalignment of the shaft. Furthermore, it has been conventional to employ roller bearings at opposite ends of the shaft. Intermediate bearings within the chamber have been tried to some extent to minimize the flexure of the shaft.
Serious problems can occur in disassembly and reassembly, as for purposes of sanitation, wherein tube scoring and blade damage can easily result as the shaft and blade assembly is moved through one end of the tube. Although elongated spacers known as "shaft skids" are available to separate the shaft and the tube so as to prevent destructive contact between the pins hinging the blades and the tube, such "skids" are not always employed and tube scoring and blade damage thus have not been effectively eliminated before this invention.